1. Field of the Invention
The present invention relates to a portable body warming device having means to controllably release heat by reaction of water with a dehydrated salt.
2. Description of the Prior Art
It is now recognized that many drownings are due to long exposure to cold water; for example, prolonged exposure in water as warm as 65.degree. F. has resulted in loss of enough body heat to cause death. The need indicated here is a simple heat source which can operate safely under water and which will start operating automatically when immersed. Having developed a device to meet this need, I discovered that there is need for body warmers in many other situations as evidenced by the various devices offered to the market in recent years and by the growing demand. It was discovered also that each of these devices has limitations and deficiencies and that various embodiments of my invention could better serve the needs in many situations.
Body warmers presently available include electrical heat sources, heat sources based on use of a combustible fuel, and chemical heat generating systems.
Electrical heat generating sources suffer disadvantages in wet environments and become ineffective. Similar disadvantages are experienced with heat sources using combustible fuels. Electrical heat sources are also relatively expensive and require a battery which may be bulky and heavy. On the other hand, it is difficult to control the heat output of devices using combustible fuels.
Chemical heat generating systems of the prior art frequently have complex construction, require agitation in use, generate heat over a short period of time, or employ expensive or objectionable chemicals and none provides an automatic start feature on immersion in water. Prior art teachings have used salts such as calcium chloride, in reaction with water; viz., U.S. Pat. No. 3,643,665, U.S. Pat. No. 3,542,032, U.S. Pat. No. 3,874,504, and U.S. Pat. No. 3,175,558. However, these teachings require mixing the water with calcium chloride in bulk without agitation. This procedure results in salt caking with uncontrollable slow heat production after an initial burst. Encapsulation has been proposed and, even if feasible for calcium chloride, would increase the cost and would result in larger volume and weight per unit of heat. The present invention overcomes these problems and provides heat sources which provide controlled output over periods of hours.